Surgical probes using either solid-state detectors or a scintillator and PMT are finding valuable application in cancer surgery. Positron emitting radioisotopes, especially FDG, have proven to be effective in identifying tumor sites. A novel probe design is described that provides for electronic collimation that can be used to locate sources of radioisotope for a variety of intra-operative surgical procedures. The electronic collimation is especially useful when used with the positron emitting radiopharmaceuticals used in PET. A computer simulation validated by experimental data will be used to generate the data necessary to prove the feasibility of the collimation method and to derive the expected performance parameters for 511 keV intra-operative localization. This new probe's 511 keV detection function would bring the option of FDG tagging into the surgical suite. PROPOSED COMMERCIAL APPLICATIONS: Improved surgical probes will have a ready in a market where radioisotope guided surgery is growing. All institutions performing oncologic surgery have a potential need for the enhanced functionality of a 511 keV sensitive probe.